Copyright @Lambda Research Corporation 2013, All Rights Reserved
Designing and Optimizing Light Guides
with TracePro
Presented by :
Lambda Research Corporation 25 Porter Rd.
Littleton, MA 01460
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Presenter: Dave Jacobsen
Senior Application Engineer Lambda Research Corporation
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Format
Today’s presentation will last approximately 30-35 minutes
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Additional Resources
•Past TracePro Webinars •http://www.lambdares.com/webinars/
•TracePro Tutorial Videos
•http://www.lambdares.com/videos/
•TracePro Tutorials
•http://www.lambdares.com/technical_support/tracepro/tutorials/
•Information on upcoming TracePro Training Classes
•http://www.lambdares.com/technical_support/training/
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Current TracePro Release
•TracePro 7.3.0 – Released Mar 7, 2013 •This release can be downloaded by anyone with a current Maintenance and Support Agreement
•www.lambdares.com
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Designing and Optimizing Light Guides with TracePro
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Webinar Topics
•Light Guide Basics
•Features and Utilities in TracePro for designing and optimizing light guides
•Using the TracePro 3D Interactive Optimizer for symmetric and asymmetric light guide profiles
•Sweeping a light guide profile along a user defined path
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Webinar Topics
•Using the new 3D Path option in the 3D Interactive Optimizer to define a sweep path in X, Y, and Z
•Defining variables and optimization targets in the Interactive Optimizer
•Setting up the TracePro model and light sources
•Light Guide design tips
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Basics
•Light guides typically guide, or direct light by total internal reflection (TIR)
•Common materials for light guides are plastic or glass
•The index of refraction of the light guide material will affect the coupling of light into the light guide and the light guiding properties
•Surface properties can be applied to a light guide to improve performance
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Basics – TIR
•Total Internal Reflection (TIR) is when light strikes a material boundary at an angle larger than the Critical Angle, relative to the surface normal, and is entirely or totally reflected, a lossless process
•TIR requires that the index of refraction of the light guide material be greater than that of the surrounding material. If this is not the case, there will be no TIR
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Basics – TIR
Light Guide with Index of Refraction of 1.5
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Basics – Critical Angle
•The Critical Angle is the incident angle of light, relative to the surface normal, at which TIR occurs
•Light at an incident angle greater than the Critical Angle is TIR’ed. Light at an angle less than the Critical Angle will be partially reflected and partially refracted out of the light guide.
•The Critical Angle varies with the indices of refraction of the light guide material and the surrounding material (typically Air)
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Basics – Calculating the Critical Angle
•The Critical Angle, θc , is calculated using Snell’s Law
•n1sinθi = n2sinθt where: •n1 = index of refraction of incident material •n2 = index of refraction of transmitted material •Θi = incident angle •Θt = transmitted angle
Image Source: Wikipedia
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Basics – Calculating the Critical Angle
•The Critical Angle, θc , can be calculated by setting θt to 90-degrees and solving Snell’s Law for θi
•Since θt = sin(90) = 1, the equation reduces to:
• θc = arcsin(n2/n1)
•Example with a typical plastic:
•n1= 1.5, n2= 1.0 (air)
•θc = arcsin(n2/n1) = 41.8°
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Basics – Calculating the Critical Angle
θi = 41.7°
θi = 41.9°
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Basics – Breaking TIR
•Sometimes we want to break TIR in a light guide to meet a performance goal, for example, a backlight or a display ring
•Two ways of breaking TIR are adding surface features or adding surface textures
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Basics – Breaking TIR
Add a physical feature to the surface of the light guide. An example would be a backlight light extractor.
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Basics – Breaking TIR
Add a texture to the surface of the light guide. An example would be a roughened surface for a indicator display.
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Basics – Etendue
•Etendue is a measure of geometrical efficiency
•G = πSsin2Ω •G = etendue •S = area of source, beam, or optic •Ω = half angle of beam
•Another useful option for fiber optics •G= πS(NA)2 - where NA is the numerical aperture of the fiber
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Basics – Etendue
•A consequence of the conservation of etendue is that by concentrating the area, the angular distribution of the illumination will spread.
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Basics – Non-TIR Light Guides
Not all light guides use TIR. An example is a hollow light guide with a reflective interior for a UV application.
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Design with TracePro
•3D modeling in TracePro
•Model compatibility with most CAD systems including SolidWorks, Pro/ENGINEER, CATIA, Inventor
•SAT, STEP, IGES import/export capability
•Accurate source models •Grid Sources •Surface Source Property •Ray Files
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Design with TracePro
•Extensive property catalogs including Material, Surface, and Surface Source
•User extendable
•TracePro Utilities •IES/LDT Analysis •Surface Source Property Generator •Texture Optimizer •2D and 3D Interactive Optimizers
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Design with TracePro
•2D and 3D Geometry Modelers available in TracePro LC – new in TracePro 7.3
•The 2D and 3D Geometry Modelers in TracePro LC have the same geometry creation capability as the Interactive Optimizers but lack the optimization feature
•2D and 3D Interactive Optimizers available in TracePro Standard and Expert editions
•This webinar will focus on using the 3D Interactive Optimizer for light guide design
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Opening
•The 3D Interactive Optimizer is launched from the Utilities Menu in TracePro
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Windows
•3 main windows visible at launch
Surface list
Property editor
Object View
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Surfaces
•Surface types available
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Surfaces
•Surface types available
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Objects
•Object types available
•Radial symmetry
•Extrusion
•Lens
•Sweep
•Biaxial
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Property Editor
•Varies depending on selection - Segment selected
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Property Editor
•Varies depending on selection - Object selected
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Radial Symmetry
Light Guide Profile
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Radial Symmetry
Profile of center “cutout” section
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Radial Symmetry
Both profiles revolved in the Object view window
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Radial Symmetry
Subtract center profile from light guide
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Radial Symmetry
Send model to TracePro
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Asymmetric Profile using Segments and Splines
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Asymmetric Profile Extruded
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Symmetric Profile using Sweep Paths
Profile of one “leg” of the light guide
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Symmetric Profile using Sweep Paths
Sweep Path of one leg of the light guide
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Symmetric Profile using Sweep Paths
Sweep Path of second leg of the light guide
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Symmetric Profile using Sweep Paths
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Symmetric Profile using Sweep Paths
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Symmetric Profile using Sweep Paths
Unite the two legs into one using the Unite command in After-scheme
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Symmetric Profile using 3D Sweep Path – New in TracePro 7.3
Light Guide profile
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Symmetric Profile using 3D Sweep Path – New in TracePro 7.3
3D path using spline segments
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Symmetric Profile using 3D Sweep Path – New in TracePro 7.3
Light guide profile swept along 3D path
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer – Examples
•Symmetric Profile using 3D Sweep Path – New in TracePro 7.3
Send model to TracePro
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Optimization
•3D Interactive Optimizer Example
Goal is to optimize the bends in the light guide for equal light at both outputs with the best efficiency
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Optimization
•Initial Irradiance Maps – 1-watt source
Leg 1 0.143 watts
Leg 2 0.164 watts
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Optimization
•Leg 1 Optimization variables – 3 spline control points
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Optimization
•Leg 2 Optimization variables – 3 spline control points
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Optimization
•Setting up the TracePro model
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Optimization
•Setting up the TracePro model – LED source
Cree XP-E white LED Surface Source Property
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Optimization
•Setting up the TracePro model - Targets
Detector1
Detector2
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Optimization
•Optimization operands
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Optimization
•Optimization Results – Optimization Log
•919 iterations
•Best result at iteration 483
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Optimization
•Optimization Results – New Sweep Paths
Leg 1 Sweep Path Leg 2 Sweep Path
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Optimization
•Optimization Results – Model in TracePro
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Optimization
•Optimization Results – Before and After Optimization
Before
After
Copyright @Lambda Research Corporation 2013, All Rights Reserved
3D Interactive Optimizer - Optimization
•Final Irradiance Maps – 1-watt source
Leg 1 0.355 watts
Leg 2 0.392 watts
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Design - Tips
•Avoid sharp corners
•Keep light guide bend radii as large as possible
•Use an accurate source model
•To improve efficiency, use scattering surfaces only where necessary
•Trace enough rays to get an accurate answer – both during optimization and in the final analysis
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Light Guide Design - Tips
•Use the Interactive Optimizers with enough variables and multiple optimization operands, uniformity and total flux for example, to improve results
•Use the analysis tools in TracePro to verify results •Irradiance/Illuminance Maps •Candela Plots •Luminance/Radiance Maps – Multiple “eye” positions if possible •Path Sorting to see ray paths
Copyright @Lambda Research Corporation 2013, All Rights Reserved
A recording of this webinar and a copy of the slides are available in the Webinars section of
our website:
http://www.lambdares.com/webinars/
Copyright @Lambda Research Corporation 2013, All Rights Reserved
Thank You
Copyright @Lambda Research Corporation 2013, All Rights Reserved
For Additional Information Please Contact:
Lambda Research Corporation
Littleton, MA 978-486-0766
www.lambdares.com